Method for cleaning road pavement



Jan. 13, 1970 M. L. THORPE 3,490,066

METHOD FOR CLEANING ROAD PAVEMENT Filed June 1, 1966 2 Sheets-Sheet I.

M. THORPE 3,490,066

METHOD FOR CLEANING ROAD PAVEMENT 2 Sheets-Sheet 2 Jan. 13, 1970 Filed June 1, 1966 United States Patent Office 3,490,066 Patented Jan. 13, 1970 3,490,066 METHOD FOR CLEANING ROAD PAVEMENT Merle L. Thorpe, Suncook, N.H., assignor to Thorpe Arc-Flame Associates, Inc., Concord, N.H., a corporation of New Hampshire Filed June 1, 1966, Ser. No. 554,389 Int. Cl. B08b 5/00, 7/00; F23c 5/00 US. Cl. 134-19 6 Claims ABSTRACT OF THE DISCLOSURE A method of cleaning a road pavement surface includes the steps of providing a combustion chamber that has a combustion product discharge orifice in the form of a series of ports. An air fuel mixture is supplied to the combustion chamber under pressure and that mixture is burned in the combustion chamber so that the combustion products are discharged through the discharge orifice in a high velocity jet. The combustion chamber is placed closely adjacent the pavement surface so that the high velocity jet impinges on the surface and dislodges non-volatilizable contaminants such as dirt and causes the rapid volatilization of other contaminants such as oil. The high velocity jet blows the removed contaminants aside and leaves the road surface in good condition for further treatment if such treatment is desired.

This invention relates to cleaning asphalt and concrete road pavements.

A primary object of the invention is to provide an improved method of removing foreign substances (e.g. oil, paint, impacted dirt, etc.) from asphalt and concrete road pavement in which a high percentage of the foreign substances are removed, without significant removal of pavement material. Other objects are to provide such a method which is low in cost, easily and reliably performed with a minimum of apparatus and manpower, and which is capable of use in removing painted road lines, cleaning the road surfaces in preparation for sealing, improving road surface traction, etc.

In general, the invention comprises the steps of providing a combustion chamber having a combustion products discharge orifice, causing a continuous discharge in the form of a high velocity jet through the discharge orifice of the high temperature products from the substantially complete combustion of an oxidant-fuel mixture in the chamber, positioning the chamber adjacent the pavement surface so that the discharge jet has a direction of propagation forming an acute forward angle to the pavement surface and a length to the point of impingement on the pavement along the direction of propagation of less than five times the width of the discharge orifice, and moving the combustion chamber along the surface generally in the direction of the apex of the acute angle while maintaining the angle and length of the jet, thereby causing the jet of combustion products to dislodge from the pavement surface non-volatilizable contaminants in the path of the jet and to cause the rapid volatilization or combustion of contaminants (such as paint and oil) in the path of the jet. The ratio of the product of the temperature of the gas jet and its velocity to the distance of the chamber discharge orifice from the pavement surface is preferably at least about where temperature is in degrees Fahrenheit and is in excess of about 3,000 F., velocity is in feet per second and is in excess of 400 feet per second, and distance is in feet. This method produces efficient contaminant removal from road surfaces in an operation that involves only superficial heating of the pavement material so that auxiliary cooling is not required; that does not require supplemental mechanical scraping; and that involves no significant adverse efiect on the pavement material itself.

A particularly advantageous use of this method is in connection with the removal of excess asphalt (the tarlike petroleum derivative which is added to crushed rocks for road surfaces) which tends to ooze and create slippery road surfaces in warm weather. For such removal 21 high temperature high velocity swath of combustion products is generated from a combustion chamber, the discharge orifice of which is maintained at a substantially constant distance from (a typical distance being one half inch), and at a fixed angle to the pavement surface is moved along the pavement surface. The excess asphalt is rapidly heated and in puddle form is blown forward by the high velocity jet swath which swath induces air However the puddle and results in ignition of the asphalt, producing combustion in diffusion flame form which may extend several feet in front of the discharge orifice and which removes the excess asphalt without impairment of the road surface. Another use of the method is in the cleaning of random cracks in pavement surfaces prior to repair with asphalt materials. In such method a single jet of high velocity combustion products is employed which removes contaminants from the crack and prepares its surfaces for receiving the asphalt repair materials.

Other objects, features, and advantages will appear from the following detailed description of particular methods of practicing the invention, taken together with the attached drawings thereof, in which:

FIG. 1 is a perspective view of apparatus used in method of the invention;

FIG. 2 is a sectional view through the combustion chamber of the apparatus shown in FIG. 1;

FIG. 3 is a section through 3-3 of FIG. 2;

FIG. 4 is a section through 44 of FIG. 3;

SIG. 5 is a perspective view of the burner cooling tube; an

FIG. 6 is a sectional view of a second form of combustion chamber particularly useful in cleaning cracks in pavement surfaces.

Apparatus for carrying out the method of the invention (FIGS. 1, 2) includes a four wheeled carriage 20 carrymg at its front a fifteen inch long combustion unit 22 mounted between carriage brackets 24, 26. Handle 28, carrying control switch unit 29, extends pivotally from the rear of the carriage and ignition and fuel control unit 30 is mounted atop the carriage. Spark plug 32 is mounted centrally along the length of the burner chamber 22 and is wired into the ignition unit 30. Fuel tubes 34, 36 (connected to common conduit 38) and coolant tubes 40, 42, extend from the ends of the burner back to supply and control apparatus carried on truck 44 which includes cooling water supply 46, air supply 48 c.f.m., 70 p.s.i. capacity), propane supply 50 (6.6 g.p.h. capacity), automatic mixture control, fuel vaporizer and safety interlock equipment 52.

The burner unit 22, comprises a cylindrical tube 54 of a high temperature alloy. Adjacent each end of the tube are three radially directed latch screws 56 which secure flame stabilizer units 58 against end surfaces 60 formed in tube 54. An end cap 62 is disposed on each end of tube 54 and bolt 64 secures that cap to stabilizer unit 58 and compresses gasket 65 to form a seal.

Each of the end caps has a tapped bore 66, communicating with port 68 which form inlets leading into the interior of the combustion chamber formed by the capped tube 54.

Each flame stabilizer unit 58 includes a hub portion 70 which is inserted into an axial bore formed in support bracket 72 of the end cap and a thin disc 74 which fits into the internal bore of cylinder 54. The disc is drilled to provide a series of apertures 78 equally spaced about the disc with the bores being at an angle to the axis of the tube, for example, 45 inwardly of the disc. Preferably each disc has seven apertures 78 on 45 centers omitting any aperture at the bottom of the disc as h wn in FIG. 4. Additionally, the stabilizer disc 74 has a pair of smaller axial apertures 80' spaced radially outwardly from and between each adjacent pair of inclined apertures 78. A row of thirty aligned cylindrical apertures forming exhaust orifices 82 over a length of ten inches are provided in tube 54 between the inner ends of the stabilizers 74.

Screw threaded couplings 84 extend from the threaded bores '66 for attachment of metal tubes 34 and 36 which communicate through common tube 38 with the fuelair mixture supply.

Soldered to the outside of the cylindrical tube 54, as by a high temperature silver solder having a melting point of at least 1100" F., is a long length of copper tubing 86 having the configuration shown in FIG. 5. An inlet end 40 of the tube proceeds downwardly around one side of the burner chamber and then longitudinally of the burner close and in parallel relation to the row of discharge orifices 82 to the other end of the burner; then upwardly on the same side of the burner and longitudinally back across the top of the burner; then around the other side of the end of the burner; back again longitudinally of the burner in parallel relation to the apertures 82 on the other side; then upwardly around the other side of the burner and to an outlet end 42.

As shown in FIG. 1, the inlet 40 and outlet 42 continue as tubes and connect to water supply 46 so that the cooling fluid may be continuously circulated through the tubing during operation of the burner.

Burner 22 is mounted and the apparatus is adjusted so that, upon ignition, substantially complete combustion of the air-fuel mixture occurs in tube 54, and a stable swath of high temperature combustion products issues at high velocity through discharge orifices 82 and impinges upon pavement surface P (FIG. 2), with the direction of propagation of the swath forming an acute (forward) angle A (FIG. 2) with the surface P. The temperature of the combustion products is substantially uniform over the width of the swath. In a preferred embodiment the swath temperature is in the order of 3000 F. and has a discharge velocity of about 900 feet per second while employing a chamber fuel pressure of three p.s.i.

In operation with a premixed combustible mixture of air and propane fiowing through the two tubes 34, 36, the spark plug 32 is momentarily energized to ignite the mixture in the combustion chamber at full flow. Substantially complete combustion of the air-fuel mixture occurs in the combustion chamber and the resulting products pass through the discharge orifices in a swath ten inches wide. The burner is passed over surface P in the general direction of the gas swath though not necessarily exactly perpendicular to the discharge orifice axis at a rate in the order of thirty feet per minute. Employing such a rate, the distance D of the chamber discharge orifices from the pavement P should be in the order of one-half inch where the velocity of the combustion products is in the range of 900 f.p.s. and the gas temperature is approximately 3000 F. Nonvolatilizable debris are dislodged from surface P, and volatilizable contaminants (e.g. paint, oil) are vaporized in the cleaning operation. An asphalt road surface, for example, treated in this manner is subjected to melting only in the upper one-sixteenth at most, the road surface immediately after the burner passes is no hotter than 150 F.; and the remainder of the asphalt is not adversely affected by the transient application of this high temperature, high velocity gaseous stream. Similar cleaning effects are produced on concrete pavement surfaces. The surface thus is 4 cleaned of contaminants without substantial adverse effect upon the pavement material itself.

A device useful in cleaning random pavement cracks preparatory to repair is shown in FIG. 6. This device includes a tubular chamber which may be metal or ceramic material capable of withstanding the combustion temperatures employed in the method of cleaning. The chamber is two inches in diameter and seven inches in length. An entrance end cap 102 is welded to the chamber 100 at one end and a nozzle cap 104 is secured to the chamber at the other end. Cap 102 includes a threaded bore 106 which receives supply pipe 108 and a passage 110 which receives ignitor spark plug 117. Nozzle cap 104 has a through passage 14 one-half inch in diameter and a cooling channel 116 has an entrance port 118 and an exit port 120. The air-fuel mixture is supplied through line 122 /8" i.p.s.) to port 118 for flow around nozzle passage 114 to cool the nozzle while preheating the combustible mixture, and then through exit port to line 108 and into the combustion chamber 100. An expansion bellows 124 allows for expansion of chamber 100 during operation of the device.

The device produces a gaseous jet of combustion products or orifice 114 that has a temperature of 3000 F. and a velocity of 3000 f.p.s. where an air-fuel mixture is supplied at a rate of thirty s.c.f.m. of air at 70 p.s.i.g. and 2.8 g.p.h. propane at 20 p.s.i.g.

While particular embodiments of the invention have been shown and described, various modifications thereof will be obvious to those skilled in the art and therefore it is not intended that the invention be limited to the disclosed embodiment or to details thereof and departures may be made therefrom within the spirit and scope of the invention as defined in the claims.

What is claimed is:

1. A method of cleaning a road pavement surface by removing paint, oil and dirt therefrom, comprising the steps of providing a combustion chamber having an integral combustion products discharge orifice,

causing a continuous discharge through said orifice in the form of a high velocity jet through the discharge orifice of the high temperature products from the substantially complete combustion of an oxidant-fuel mixture in said chamber,

positioning said chamber closely adjacent said surface so that said discharged jet has a direction of propagation forming an acute angle to said pavement surface, and

moving said combustion chamber along said surface thereby causing said combustion products to dislodge from said pavement surface non-volatilizable contaminants in the path of said jet and to cause the rapid volatilization and the combustion of contaminants in the path of said jet in a removal operation without significant adverse effect on the pavement material itself, the distance of said chamber and said discharge orifice from said pavement being maintained less than five times the width of said discharge orifice.

2. The method of claim 1 wherein said jet temperature is in the order of 3000 F. and said jet velocity is in excess of 400 feet per second.

3. The method as claimed in claim 1 wherein the ratio of the product of the temperature of the gas jet and its velocity to the distance of the chamber discharge orifice from the pavement surface is at least about 10 where temperature is in degrees Fahrenheit and at least about 3,000 F., velocity is in feet per second and in excess of 400 feet per second, and distance is in feet.

4. The method as claimed in claim 3 wherein said combustion chamber orifice extends linearly along a substantial axial extent of the wall of said chamber, and said jet of combustion products is formed in a swath of length substantially equal to said axial extent and said swath is of substantially uniform temperature over its entire length,

and said distance is maintained substantially constant as said chamber is moved along said pavement surface. 5. A method of removing paint, oil and dirt from the surface of a road pavement comprising the steps of:

providing a combustion chamber having an integral combustion product discharge orifice, supplying an air fuel mixture under pressure to said combustion chamber, burning said air fuel mixture in said chamber so that the combustion products are discharged through said discharge orifice in the form of a high velocity jet, positioning said chamber closely adjacent said surface so that said discharged jet has a direction of propagation forming an acute angle to said pavement surface, and moving said combustion chamber along said surface thereby causing said combustion products to dislodge from said pavement surface non-volatilizable material in the path of said jet and to cause the rapid volatilization and of the combstion of volatilizable material in the path of said jet in a removal operation without significant adverse effect on the pavement material itself, the distance of said chamber and said discharge orifice from said pavement being maintained less than five times the width of said discharge orifice. 6. The method of claim 5 wherein said jet temperature is in the order of 3000 F. and said jet velocity is in excess of 400 feet per second.

References Cited UNITED STATES PATENTS Healy et al. 126271.2 King 126271.2 Porter 126271.2

Schultz 126271.2 Elze 126271.2

Littleford 126271.2

Davis 126 271.2 Deck.

Feldman et al.

Moench 126271.2

Schultz 126271.2

Allen 126--110 Zimmerman 126271.2

Wetzel 3719 Wilson 126271.2 Wilson 126271.2

Wilson 126271.2

0 MORRIS O. WOLK, Primary Examiner JOSEPH T. ZATARGA, Assistant Examiner US. Cl. X.R. 

